WALTHAM — Forty-eight hours after losing their All-Star point guard, their floor leader, and their funniest practice personality, the Celtics worked out Tuesday, with the atmosphere at the Sports Authority Training Center rife with uncertainty.

The Celtics have played without Rajon Rondo before, when he was battling nagging injuries or during NBA suspensions, but the finality of his absence this season because of a torn right anterior cruciate ligament seemed official when he was not on the practice court.

There were no new additions besides rookie center Fab Melo, who was recalled from NBADL Maine and may actually get a chance to play in an NBA game. Besides Melo, the Celtics were the same Rondoless club that defeated the Miami Heat in double overtime Sunday.

Coach Doc Rivers said Courtney Lee will start at guard alongside Avery Bradley, who will move to Rondo’s position at the point. Other than that, the Celtics are going to stand pat for now; although Rivers said he has encouraged former Celtic Keyon Dooling to get into shape for a possible return.

“He would be the closest for me if we had to go in another direction [at point guard],” Rivers said. “We’d have to find out if he could still do it. He knows our stuff. He’s the easiest by far. He’s going to [get in shape] anyway.”

But Rivers said the Celtics don’t plan to make any sudden moves. He wants to see how his stockpile of guards does in Rondo’s absence.

“I don’t sit down and whine about it,” Rivers said. “No one is going to listen, clearly not the other team. But I do think we can be really good. We’ll be a little different but I think we can be really good because I like the guys on our team.”

Rivers has maintained all season that he likes his team, but his patience has slipped with their inconsistency in the weeks before Rondo’s injury. Losses to New Orleans, Chicago, Detroit, Cleveland, and the double-overtime heartbreaker to Atlanta (in which Rondo was injured) had Rivers threatening roster moves.

Now, he said, the organization must exhibit even more patience.

“There literally is no different roles,” Rivers said. “I don’t want a guy to now think he’s Rondo. Everyone’s going to play the same role. The only different thing is someone else is going to bring the ball up and then pass it. That’s the difference.

“It’s just basketball. There’s no point guard. It’s just basketball by committee.

“There’s a lot of adjustments, but you have to be careful with your play calling. You simplify it. You let them play through space.”

The floor leadership may shift back to Kevin Garnett and Paul Pierce, where it did before Rondo became an All-Star. They said the transition won’t be easy.

“Everybody knows the responsibility is going to fall on multiple people,” Garnett said. “To be honest with everybody here, I think everybody after Sunday was in a fog almost, almost stop playing, stop [expletive] type thing and just settling in.

“I think everybody is really trying to put their arms around the concept that he’s actually hurt, hurt to the point where he can’t play. That’s what’s got everybody bewildered, even him.

“He came in this morning and I saw him and it was like unreal. The fact is that it is real. We have to pick up the pieces and carry ourselves. I think there’s going to be honestly an adjustment period, now that we know he’s going to be out.”

Rivers said the Celtics will rely more on ball movement and less on the fast break. Leandro Barbosa and Jason Terry are not natural point guards but will do more ball-handling. And Rivers expects opponents to apply more ball pressure because the Celtics lack a natural point guard.

“I’ve been ready, and if he needs me, I’ll be there for the help,” Barbosa said. “I don’t know what’s going to happen. Now is a totally different situation for the whole team.

“I’ll say, almost my whole career, especially when I was with the Phoenix Suns, I was playing a lot of point guard to back up Steve Nash. I’m not Rajon Rondo. My game is totally different from his game.”

Entering Wednesday’s game against the Kings, there is more uncertainty than expectations. The Celtics are currently the eighth-seeded team in the Eastern Conference, but are just six games behind third-seeded Chicago. There is plenty left to play for, but the players understand that will mean reinventing themselves.

“You really don’t replace a Rondo,” Pierce said. “It’s hard to replace an All-Star guard. It’s just about understanding what the team needs. It’s something I’ve been doing for years, understanding what the team needs on any given night. I’m anxious to see how this thing works out.”